1. Field of the Invention
The present invention generally relates to a tone synthesizing apparatus and a tone parameter setting apparatus suitable for use in an electronic musical instrument.
2. Description of Related Art
In a known electronic musical instrument, a variety of plug-in boards can be attached to a mother board of a main frame of the electronic musical instrument. In personal computers also, a variety of plug-in boards can be attached to the mother board of the main frame. In personal computers, after inserting a plug-in board, it is a general practice to install driver software from a CD-ROM or a floppy disk for operating the inserted plug-in board. Like personal computers, an auxiliary storage device such as a CD-ROM drive or a floppy disk drive may be attached to electronic musical instruments. However, increased cost prevents many of electronic musical instruments from installing the auxiliary storage device. Therefore, a serious problem lies in that a plug-in board having capabilities that have not been supposed at designing the main frame of the electronic musical instrument cannot make the use of or at least cannot make the most of these capabilities of the plug-in board.
As described above, there are known electronic musical instruments in which a variety of plug-in boards can be attached to the mother board of these electronic musical instruments. The mother board herein denotes a main circuit board installed on an electronic musical instrument beforehand. If no plug-in board is attached, the mother board may simply provide basic capabilities. On the other hand, a plug-in board is attached to the mother board afterward to provide capabilities additional to these basic capabilities. For example, a plug-in board provides a tone generator that can create a timbre by an algorithm of higher level than that of the mother board. When performance information such as a MIDI signal is externally supplied to the mother board while such a plug-in board is attached, the mother board determines which of the mother board and the plug-in board should treat this performance information. This decision is implemented by memorizing the name of the board by which the sounding is to be made into a table beforehand in correspondence with timbre names, for example. Needless to say, only the performance information to be sounded by the plug-in board is supplied to the plug-in board. However, according to the above-mentioned technology, the decision in the mother board must be made before the supplied performance information reaches the plug-in board, so that the arrival of this information involves some delay. This causes a timing deviation between sequential music tones, thereby presenting a problem of adversely affecting the music tones.
An electronic musical instrument is known, in which a variety of plug-in boards can be attached to the mother board of the main frame through extension slots. The mother board is a main board installed in the electronic musical instrument beforehand. If no plug-in board is attached, the mother board provides basic capabilities alone. The plug-in board can be additionally attached to the mother board, providing capabilities additional to the basic capabilities of the mother board. For example, a plug-in tone generator board increases the number of timbres that can be sounded. A plug-in effect board increases the number of selectable sound effects. However, in the conventional electronic musical instruments, the extension slots for installing plug-in boards are each dedicated to a tone generating board or an effect board. Therefore, it is impossible to freely insert a plug-in board in arbitrary one of the extension slots. In contrast, in personal computers, a plug-in board can be inserted in any extension slot. The plug-in board thus inserted can be operated by driver software installed from a CD-ROM or a floppy disk. It would be also practical for electronic musical instruments to have the common extension slots similar to those of personal computers. However, this presents a problem of increase in fabrication cost. Further, a sound generating system is typically composed of a block for generating tones, a block for mixing generated tones, a block for imparting an effect to the mixed tones and other blocks, thereby making it difficult to insert a plug-in board freely at desired position of the tone generating system.